Although not an area of my research, I've always found computer
languages to be fascinating as well, especially functional
languages and domain-specific
languages ("little languages"). Functional and domain-specific
languages are important because they can have greater expressivity
than well-known general-purpose languages like C/C++/Java, leading
to greater productivity for the programmer.

I also have some interest in data structures and memory management
(see my bin-arrays data
structure [I need a better name], which is a kind of special-purpose
memory manager for efficiently working with a large number [tens of
millions] of doubly-linked lists).